Protection of Polynucleotide Phosphorylase by Substrates against Urea Inactivation

Abstract

Polynucleotide phosphorylase from Escherichia coli is irreversibly inactivated by preincubation with urea at concentrations of 3.0 M or greater. The addition of ribonucleotide polymers, oligonucleotides or nucleoside diphosphates to the preincubation medium markedly decreases the rate of this inactivation. Both oligonucleotides terminated with an unesterified 3′-hydroxyl group or esterified with a 3′-phosphate are equally effective.